The superior cervical ganglia (SCG) of rats ranging in age from 4 to 35 months were examined by light and electron microscopy. The specimens were fixed by perfusing the rats with a buffered aldehyde fixative, the ganglia removed, post-fixed, dehydrated, and embedded in epoxy. Thick sections were stained with toluidine blue for light microscopy, while thin sections for electron microscopy were stained with uranyl acetate and lead citrate. The ganglion cells of young animals contained cytoplasmic lysosomes, most of which would be classified as primary. With increasing age, lipofuscin began to accumulate, often confined to one region of the cytoplasm. Neurozxonal Dystrophy (NAD) was a striking feature of older rats. The NAD was characterized by arrays of membranes, patches of electron lucent material, and mitochondria in the condensed configuration. Nuclear inclusions were present in the ganglion neurons of aging animals as well. In comparing the NAD found in the superior cervical ganglion with NAD seen in our studies of the central nervous system, we observed that the membrane arrays of the SCG were different in morphology from arrays seen in the dorsal column nuclei of aging mice. Secondly, mitochondria of NAD in the dorsal column nuclei were enlarged, while mitochondria of NAD in the SCG tended to be condensed. Our studies thus indicate that Neuroaxonal Dystrophy, although a single classification of neurological deterioration which affects every vertebrate, including man, must be sub-classified according to the particular nervous system region under study.